docs: def init_app(self, app):
          """
          Mutate the application passed in as explained here:
          http://flask.pocoo.org/docs/0.10/extensiondev/
  
          :param app: Flask application
          :return: None
          """
  
          # Setup a few sane defaults.
          app.config.setdefault('WEBPACK_MANIFEST_PATH',
                                '/tmp/themostridiculousimpossiblepathtonotexist')
          app.config.setdefault('WEBPACK_ASSETS_URL', None)
  
          self._set_asset_paths(app)
  
          # We only want to refresh the webpack stats in development mode,
          # not everyone sets this setting, so let's assume it's production.
          if app.config.get('DEBUG', False):
              app.before_request(self._refresh_webpack_stats)
  
          if hasattr(app, 'add_template_global'):
              app.add_template_global(self.javascript_tag)
              app.add_template_global(self.stylesheet_tag)
              app.add_template_global(self.asset_url_for)
          else:
              # Flask < 0.10
              ctx = {
                  'javascript_tag': self.javascript_tag,
                  'stylesheet_tag': self.stylesheet_tag,
                  'asset_url_for': self.asset_url_for
              }
              app.context_processor(lambda: ctx)